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Brian's Photo Blog — Article 256
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Olympus TG-2 Converter Lenses Sample Images
Tuesday 25 June 2013   —   Category: Equipment
This is the third in a series of articles exploring the capabilities of my new Olympus TG-2 “tough” pocket camera. If you missed the other articles, you can view a list of them here.

In my last article, I gave you an introduction to the Olympus TG-2 converter lenses. Today I will show you some sample images I took with these lenses — and I have so much to share with you! But if you are in a hurry and don’t want to read all the details, you can skip down to the summary.

To start off with, let’s look at the TG-2’s built-in 4x zoom lens: the native focal length is 4.5mm to 18mm, which is a 35mm equivalence of 25mm to 100mm. If you do the math, you come up with a focal length multiplier (FLM) of 5.56 (100 ÷ 18). In descriptive terms, this lens is a fairly wide-angle to a medium telephoto focal-length range.

In some circumstances I may want a wider wide-angle, or a longer telephoto. Normally I would be out of luck when using a point-and-shoot camera — what’s built in is what I get and ONLY what I get. But with the converter lenses I reported on in the previous article, I've got options which are otherwise unavailable. Three cheers for Olympus!

IMAGE 1 — The TG-2’s built-in lens at 1x zoom, 25mm.
IMAGE 2 — The FCON-T01 fisheye converter lens at 1x zoom,
19mm or 14mm (see article text for explanation).
In order to simplify things in the following discussion, I’m going to refer to all focal lengths in their 35mm equivalence. In addition, all of the following photos were taken from the exact same tripod position, and the camera was not moved while changing lenses.

IMAGE 1 to the right is a picture of my backyard taken with the built-in lens at its 1x zoom setting, which corresponds to a 25mm focal length. This will be the reference IMAGE used to compare the following photos taken with the fisheye converter lens.

Speaking of which, IMAGE 2 was taken with the FCON-T01 fisheye converter lens attached, at the camera’s 1x zoom setting. Unfortunately, nailing down the exact focal length is going to be challenging and open to interpretation. Let me explain....

According to the EXIF metadata as displayed by Adobe Lightroom, the native focal length was 3.33mm, with a corresponding 35mm equivalence of 18mm. According to Olympus' product info, the 35mm-equivalent focal length is 19mm. Well, I suppose a measly 1mm difference in focal length isn’t too serious!

In order to try to get a more accurate answer, I set up my Olympus OM-D E-M5 camera with a Panasonic 7-14mm (14-​28​mm equivalent) lens on a tripod in roughly the same location and took some test shots at different focal lengths. Once I got the images back into my computer, I first tried to find which test photo had the same angle of view as IMAGE 2 — this turned out to be the one with a 14mm focal length. Therefore, I determined that the focal length of the TG-2 camera at 1x zoom changes from 25mm to 14mm when the fisheye converter lens is attached.

But not so fast! I then noticed that although the angle of view matched, the size of the bench in the two photos did not match at all. So, after going through all of the test images again, the one with a bench size that matched the bench size in IMAGE 2 was the one with a focal length of 19mm — which matches what Olympus states in its specs.

In light of these confusing results, the exact focal length of the fisheye converter lens at 1x zoom depends on what criteria you use. Based upon the angle of view, I would say that the focal length is around 14mm. But based upon the apparent magnification, I would say that the focal length is around 19mm. Take your pick!

IMAGE 3 — The same photos as IMAGE 2, with Adobe Lightroom’s distortion correction applied at 100%.
IMAGE 4 — The FCON-T01 fisheye converter lens
at 4x zoom, 74mm.
IMAGE 5 — The TG-2’s built-in lens at 4x zoom, 100mm.
IMAGE 6 — The TCON-T01 telephoto converter lens at
4x zoom, 170mm.
IMAGE 7 — The TCON-T01 telephoto converter lens
at 1x zoom, 42mm.
IMAGE 8 — The TCON-T01 telephoto converter lens
at 3x zoom, 127mm.
In IMAGE 2 you will notice that there is a lot of barrel distortion — in reality, the basketball pole is not bent like that, and the edge of the grass at the bricks is straight and not curved. I suppose that’s the main reason Olympus named this converter lens a fisheye rather than simply an ultra wide-angle.

So, using the distortion correction capabilities of Lightroom I tried to fix this problem, but even at the full 100% setting, it could not remove all of the distortion. However, it is somewhat improved — curved lines are now straighter — as you can see in IMAGE 3.

The FCON-T01 fisheye converter lens can be used throughout the entire 4x zoom range of the TG-2 camera. IMAGE 4 was taken at the 4x zoom setting, and according to the image’s EXIF data, the native focal length was 13.33, with a 35mm equivalence of 74mm. I didn’t do any testing in this case to determine if 74mm is accurate or not — we’ll just take the camera’s word for it.

Because the TG-2 is not an interchangeable-lens camera, you may wonder how the camera knows a converter lens is attached, so it can put the correct information in the EXIF data. I’m glad you asked! In the camera’s menu system, there is a screen where you can choose which lens is attached, as shown below:
The camera also uses this setting so that, if you have the telephoto converter lens attached, when you turn the camera on, it automatically zooms to the 4x setting. Which leads us to our next lens and our next set of photos....

As before, I will be using the built-in lens as a baseline reference for the TCON-T01 telephoto converter lens. IMAGE 5 was taken with the built-in lens at its maximum optical telephoto 4x zoom setting, which corresponds to a 100mm focal length.

After attaching the telephoto converter lens and setting the proper option on the camera’s Accessory Settings menu, the EXIF data for the resulting photo — IMAGE 6 — shows a native focal length of 30.6mm, with a 35mm equivalence of 170mm. This significant increase in focal length can come in quite handy for those shooting occasions when you need that extra reach.

Unlike the fisheye converter lens, this telephoto converter can NOT be used throughout the entire 4x zoom range of the TG-2 camera. As IMAGE 7 clearly demonstrates, this lens is totally unusable at the 1x zoom setting — unless, of course, you are wanting that particular effect for some odd reason. It is not until you get to a zoom setting of around 3x (or perhaps slightly less if you really want to push it) that the entire frame contains a usable image while using the telephoto converter lens, as seen in IMAGE 8.

So, in summary:
  • The Olympus TG-2 camera’s built-in lens has a 4x optical zoom with a 35mm equivalent focal length of 25mm to 100mm.
  • With the FCON-T01 fisheye converter lens attached, the entire 4x zoom range is still usable, and there is a 0.74x reduction in magnification, with a 35mm equivalent focal length of 18.5mm to 74mm. Because it is a fisheye lens, there is noticeable barrel distortion, particularly in the lower zoom range.
  • With the TCON-T01 telephoto converter lens attached, only the 3x to 4x zoom range is still usable, and there is a 1.7x increase in magnification, with a 35mm equivalent focal length of 127mm to 170mm.
The TG-2’s built-in lens also has some significant macro capabilities, which I will explore in a future article.
Brian's Photo Blog — Article 256
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Reader Comments
On April 8, 2014, Chad wrote:
Thanks for posting these images. I was curious about the Fisheye lens and what corrected images would look like. I played around with GIMP's Len Distortion tool to produce corrections that preserve straight lines. You can find your original image and my corrected image here: http://s1117.photobucket.com/user/ccpeckiii/library/Olympus%20FCON-T01

This was only a quick and dirty effort. Better results would require a high resolution image or images and more time. Anyway here are the parameters I used: Main=-73.568, Edge=29.515.
On April 8, 2014, Chad wrote:
I found I can get much better results using the zoom parameter also. The fisheye achieves the equivalent of an 12mm lens using these parameters: main=-77.093, edge 25.110, zoom=-17.181. Images can be found in the same place: http://s1117.photobucket.com/user/ccpeckiii/library/Olympus%20FCON-T01

A final note: using cropping instead of relying fully on the zoom parameter, you can preserve even more of the image. Parameters:Main=-95.595, Edge=33.921, Zoom=-41.85

Very impressive!
On April 22, 2014, Norman wrote:
Thanks for this post! It was very helpful.

Norman from Poland.
 
Brian's Photo Blog — Article 256
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